|
| Techniques used to improve the performance of SAHs and their types | Studies | Years |
| Methods | Types/description of the method |
|
| Heat storage materials | Sensible heat storage materials (water, pebble, bed, sand, gravel, metal chips, and concrete) | Murali et al. [117], Kalaiarasi et al. [17], Vijayan et al. [118], Ayyappan et al. [119], and Kalaiarasi [76] | 2015-2020 |
| Latent heat storage materials (PCM): paraffin wax, Glauber’s salt, eutectics of organic and nonorganic compounds, and fatty acids | Javadi et al. [120], Karthikeyan et al. [121], SunilRaj and Eswaramoorthy [122], Raj et al. [123], Sharma et al. [124], Mahmoud et al. [125], and Jawad et al. [126] | 2020 |
| Absorber coating | Nonselective coating and selective coating | Abdelkader et al. [127] and Kumar et al. [128] | 2019-2020 |
| Packed bed | Single-pass packed bed | Dhiman and Singh [129] and Singh [130] | 2015-2020 |
| Double-pass packed bed | Singh et al. [131], Singh [130], Dosapati and Mandapati [132], Roy and Hoque [133], Chouksey and Sharma [134], Priyam et al. [135], Singh and Dhiman [136], and Mahmood et al. [137] | 2015-2020 |
| Fins or corrugated surfaces | Longitudinal fins, attaching baffles, and corrugated fins | Kumar and Chand [138], Handoyo et al. [139], Aboghrara et al. [140], Kabeel et al. [141], Darici and Kilic [142], Priyam and Chand [105], Lin et al. [143], and Zheng et al. [144] | 2015-2020 |
| Roughness geometry | Coarse transverse rib | Singh et al. [145], Singh and Singh [146] | 2015-2020 |
| Coarse V-rib | Nidhul et al. [99], Jain and Lanjewar [147], Singh and Lanjewar [148] | 2015-2020 |
| Coarse transverse wedge-shaped rib | Bhagoria et al. [149] | 2002 |
| Coarse rib-grooved | Jaurker et al. [150] | 2006 |
| Coarse metal grit rib | Karmare and Tikekar [151]–[153] | 2007-2010 |
| Coarse arc-shaped rib | Ghritlahre et al. [154], Kumar et al. [155], Ghritlahre and Prasad [156], Sahu and Prasad [157], Saravanakumar et al. [158, 159], and Yadav and Prasad [160] | 2015-2020 |
| Coarse discrete W-shaped rib | Jain et al. [161] | 2017 |
| Coarse multi-V-rib | Jin et al. [162], Kumar and Kim [163] | 2015-2020 |
| Coarse W-shaped rib | Patel and Lanjewar [164], Thakur and Thakur [165] | 2015-2020 |
| Coarse discrete V-down rib | Singh et al. [166] | 2012 |
| Staggered ribs connected coarse broken V-rib | Patil et al. [167, 168] | 2010-2015 |
| Coarse dimple-shaped rib | Sethi et al. [169] | 2012 |
| Coarse circular protrusions organized circular arc rib | Yadav et al. [170] | 2013 |
| Coarse gap multi-V-shaped rib | Kumar et al. [171] | 2013 |
| Coarse multi-arc-shaped rib | Singh et al. [172] | 2014 |
| Coarse V-rib connected symmetrical gaps | Maithani and Saini [173]–[175] | 2015-2020 |
| Coarse staggered rib linked multigap V-down ribs | Deo et al. [176] | 2016 |
| Coarse reverse L-shaped rib | Gawande et al. [87] | 2016 |
| Coarse gaps linked multiple arc-shaped rib | Pandey et al. [177] | 2016 |
| Coarse broken arc rib | Gill et al. [88] and Hans et al. [178] | 2015-2020 |
| Staggered rib piece connected broken arc rib | Gill et al. [179] | 2016 |
| “S”-shaped pattern organized arc-shaped ribs | Kumar et al. [180] | 2017 |
| Dimpled barrier multiple type V-pattern rib | Kumar et al. [181] | 2017 |
| Hyperbolic ribs | Thakur et al. [90, 182] | 2015-2020 |
| Inclined upper part connected rectangular stopper rib | Menasria et al. [183] | 2017 |
| Wobbled multiple V-shaped ribs | Jin et al. [184] | 2017 |
| Thin truncated ribs | Sharma and Kalamkar [185] | 2017 |
| Helical or spiral flow path | SAH with helical flow paths | Heydari and Mesgarpour [111], Bezbaruah et al. [113], and MesgarPour et al. [110] | 2018-2020 |
| SAH with the spiral shape of spoilers | Jia et al. [112] | 2018 |
| SAH equipped with helical coiled inserts | Singh and Vardhan [114] | 2019 |
| SAH integrated with helical tubes carrying PCM | Saxena et al. [115] | 2020 |
| SAH tube with helical corrugation and perforated circular disc inserts | Bhattacharyya et al. [116] | 2020 |
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